This invention relates to an apparatus for limiting the working stroke of a cutting or blank holding ram in mechanically operated presses with particularly combined cutting and drawing tools, as well as with elastic pads disposed in the respective ram pressure points (centers).
It is necessary in such presses, after a cutting step has been executed, for the respective blank holder, which can be the cutting ram proper or which can be connected to such cutting ram, to have an exactly defined dwell (rest) phase in the press cycle, during which the drawing operation following the cutting step is accomplished. While this dwell phase can be provided with sufficient accuracy in so-called universal presses by an appropriate selection of the universal joint system, this is not the case in eccentric presses, as is well known.
Therefore, it is an object of this invention to find ways and means to obtain even and especially in case of the lastmentioned press types, a dwell phase of the stamping or blank holding ram.
To attain this object, the present invention suggests to arrange, in the tool zone, stops for the cutting or blank holding ram and to associate the respective ram pressure points with at least one storage zone for receiving the elastic pads which have been displaced and/or temporarily deformed after the ram has met with the stops.
These stops are adjustable with respect to their level and are arranged symmetrically with respect to the associated ram. The required storage space can be provided within the ram proper or outside of the ram according to different contemplated preferred embodiments of the present invention.
The mode of operation of the apparatus according to this invention is such that the cutting or blank holding ram, after meeting with the stops, is arrested already prior to reaching its lower dead center position effected by the drive means, while the drive piston (connecting) rods of the ram continue their operation and dip into the elastic pads. During this immersing time, wherein thus the stamping or blank holding ram is perforce in the rest position due to its meeting with the stops, the so-called overshoot stroke (overtravel) of the ram is absorbed in the ram pressure point, and the thus-displaced or temporarily deformed elastic pad is displaced into the associated storage spaces.
In this connection, it is contemplated by the present invention to employ as the elastic pad several types of mechanical elements, such as springs or the like. In particularly preferred embodiments it is contemplated to arrange deformable masses and/or pressure fluid cushions in the ram pressure point.
In addition to providing an accurately defined immersion (plunging) time, i.e. dwell phase, another advantage of the arrangement according to this invention resides in that the level adjustability of the stops affords the possibility of smaller ram adjustments without having to utilize complicated adjustment mechanisms for this purpose.
These and further objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, a single embodiment in accordance with the present invention.